REPORT OF COMMISSIONERS OF INLAND FISHERIES. 89 



of the basiopodite it is seen that this breaking plane is obviously the 

 most favorable region of the cheliped for autotomy. Not only is it 

 one of the narrrowest cross sections of the limb, but the external 

 groove is continued inwards by a double membraneous plate, which 

 readilj^ separates when the limb is voluntarily dropped off, leaving 

 one membrane upon the leg and one on the remaining stump. Fig. 

 II, 4, shows this membrane extending almost entirely over the basiop- 

 odite — it is perforated only at the center by an artery, the blood 

 sinuses, and a large nerve. It is remarkable that the nerve and 

 blood vessels may be thus suddenly snapped off leaving the stump 

 as clean as though it were cut with a sharp knife. 



In the case of the ambulatory appendages or walking legs, the 

 second and third segments (Fig. Ill, is, bs.) are not fused as in the 

 chelipeds, but the legs are always thrown off at the joint between 

 these two segments (Fig. Ill, 1). Throughout the organism the 

 power of autotomy has been observed to exist only in the chelipeds 

 and the four pairs of walking legs. 



When the limb has been thrown off a dense blood clot immediately 

 forms over the broken surface of the stump. Within a few days a 

 small white papilla appears near the center of this dot which soon 

 develops into the bud of a new limb. The time which intervenes 

 between autotomy and the appearance of the new bud varies with 

 several conditions which will be referred to later, such as the age of 

 the lobster and the moulting period, etc. Fig. IV, Plate XXII, 

 shows the basiopodite of the first left leg of a 7i inch lobster, on which 

 the regenerating bud of three millimeters has appeared within about 

 fifteen days after autotomy. In the same number of days a fourth 

 or fifth stage lobster will often have reproduced an entire appendage. 



The bud continues to increase in size, sometimes becoming more 

 than an inch in length. Fig. I (1), Plate XXI, shows the regener- 

 ating bud of the left cheliped of a 7^ inch lobster which measured 

 If inches just before moulting. Throughout this process the bud is 

 ahvays inclosed within a membraneous cuticular sac. In the latter 

 part of the development constrictions begin to appear upon the bud 



